The dyes 1-ethyl-2-(3-(1-ethylnaphtho(1,2d)thiazolin-2-ylidene)-2-ethyl-propenyl)naphtho( 1,2d)thiazolium bromide, Ethyl-Strains-all, and 1-ethyl-2-(3-(1-ethylnaphtho(1,2d)thiazolin-2-ylidene)-2-methylpropenyl) naphtho(1,2d)-thiazolium bromide, Stains-all, are metachromatic dyes of unusual sensitivity for differentiating various classes of macromolecules by color. Proteins, phosphoproteins, sialoglycoproteins, glycosaminoglycans and nucleic acids stain differentially in tissue sections and on polyacrylamide gels following electrophoresis. The dyes differ in staining properties, particularly with respect to staining macromolecules in tissue sections. Of these two stains, Ethyl-Stains-all is more useful for distinguishing a wide variety of macromolecules.